Classification of Green Algce. 115 
zoospores, or by the conjugation of isoplanogametes, or rarely 
heterogamous; sometimes by fragmentation of the thallus or by 
aplanospores. 
(a) SIPHONE1/E. Thallus of a single ccenocyte, rarely 
seccndarily septate except in connection with the formation of repro¬ 
ductive organs. All the forms except Pvotosiption are marine. 
Fam. I. Protosiphonace^e. Thallus consisting of a simple tubular 
or bladder-shaped shoot attached below by a simple or slightly branched 
colourless root. 
[It is probable that the two genera we have included in this family 
have no close affinity, but they are conveniently classed together as two 
of the simplest expressions of the Siphoneous tendency.] 
Genera. 
1 . Protosiphon. Klebs, 1896 . 
Shoot spherical to tubular, with a reticulate parietal 
chror/iatophore containing several pyrenoids. Root 
a direct continuation of the shoot and absorbing 
water from the soil in accordance with the terrestrial 
habit. Reproduction by division of the entire young 
ccenocyte, or by the budding off of new individuals from 
the shoot, or by division of the contents of the shoot 
into ( 1 ) facultative isogametes, or ( 2 ) aplanospores 
which may either germinate directly or themselves 
become gametangia. The alternative methods of 
reproduction are directly determined by external 
conditions. 
2 . Codiolum. A. Braun, 1852 . 
Shoot club-shaped. Root without a cavity, in accord¬ 
ance with its aquatic (marine) habitat. Reproduction 
by aplanospores or binagellate swarmers. 
Fam. II, Bryopsidace/E. 
Thallus a branched ccenocytic tube. Basal branches developed 
as fixing organs (roots). Shoot consisting of a main ascending axis 
(“stem”) which bears branches of both limited and unlimited growth 
(“■leaves” and axes of the second order). Chloroplasts numerous, small, 
flat, ellipsoidal, each with one pyrenoid. 
Reproduction by the conjugation of planogametes produced in 
leaves which are shut off from the stem by secondary septa. 
Genus. 
Bryopsis. Lamouroux, 1809 . 
Branches and leaves arranged distichously on the axis. 
Anisogametes. Plants dioecious. 
Fam. III. DERBESIACEiE. 
Thallus a simple or slightly branched tubular coenocyte. No 
differentiation into stem and leaves. Chloroplasts oval, discoid, with or 
without pyrenoids. 
Reproduction by zoospores, produced in spherical or club-shaped 
lateral branches of limited growth. Zoospores rounded , with a crown 
of cilia at the colourless anterior end. 
